docs: def to_numpy(self):
          """
          Convert this matrix into a
          `numpy.matrix <http://docs.scipy.org/doc/numpy/reference/generated/numpy.matrix.html>`_.
          """
          import numpy as np
          cols, rows = self.GetNcols(), self.GetNrows()
          return np.matrix([[self(i, j)
              for j in range(cols)]
              for i in range(rows)])